1 files changed, 27 insertions, 7 deletions

diff --git a/src/library_browser.js b/src/library_browser.js
index fbc609d7..458a8dd2 100644
--- a/src/library_browser.js
+++ b/src/library_browser.js
@@ -252,7 +252,7 @@ mergeInto(LibraryManager.library, {
 
           var errorInfo = '?';
           function onContextCreationError(event) {
-            errorInfo = e.statusMessage || errorInfo;
+            errorInfo = event.statusMessage || errorInfo;
           }
           canvas.addEventListener('webglcontextcreationerror', onContextCreationError, false);
           try {
@@ -319,7 +319,7 @@ mergeInto(LibraryManager.library, {
         }, false);
       }
       if (setInModule) {
-        Module.ctx = ctx;
+        GLctx = Module.ctx = ctx;
         Module.useWebGL = useWebGL;
         Browser.moduleContextCreatedCallbacks.forEach(function(callback) { callback() });
         Browser.init();
@@ -478,19 +478,30 @@ mergeInto(LibraryManager.library, {
         // in the coordinates.
         var rect = Module["canvas"].getBoundingClientRect();
         var x, y;
+        
+        // Neither .scrollX or .pageXOffset are defined in a spec, but
+        // we prefer .scrollX because it is currently in a spec draft.
+        // (see: http://www.w3.org/TR/2013/WD-cssom-view-20131217/)
+        var scrollX = ((typeof window.scrollX !== 'undefined') ? window.scrollX : window.pageXOffset);
+        var scrollY = ((typeof window.scrollY !== 'undefined') ? window.scrollY : window.pageYOffset);
+#if ASSERTIONS
+        // If this assert lands, it's likely because the browser doesn't support scrollX or pageXOffset
+        // and we have no viable fallback.
+        assert((typeof scrollX !== 'undefined') && (typeof scrollY !== 'undefined'), 'Unable to retrieve scroll position, mouse positions likely broken.');
+#endif
         if (event.type == 'touchstart' ||
             event.type == 'touchend' ||
             event.type == 'touchmove') {
           var t = event.touches.item(0);
           if (t) {
-            x = t.pageX - (window.scrollX + rect.left);
-            y = t.pageY - (window.scrollY + rect.top);
+            x = t.pageX - (scrollX + rect.left);
+            y = t.pageY - (scrollY + rect.top);
           } else {
             return;
           }
         } else {
-          x = event.pageX - (window.scrollX + rect.left);
-          y = event.pageY - (window.scrollY + rect.top);
+          x = event.pageX - (scrollX + rect.left);
+          y = event.pageY - (scrollY + rect.top);
         }
 
         // the canvas might be CSS-scaled compared to its backbuffer;
@@ -764,6 +775,15 @@ mergeInto(LibraryManager.library, {
         return;
       }
 
+      // Signal GL rendering layer that processing of a new frame is about to start. This helps it optimize
+      // VBO double-buffering and reduce GPU stalls.
+#if FULL_ES2
+      GL.newRenderingFrameStarted();
+#endif
+#if LEGACY_GL_EMULATION
+      GL.newRenderingFrameStarted();
+#endif
+
       if (Module['preMainLoop']) {
         Module['preMainLoop']();
       }
@@ -863,7 +883,7 @@ mergeInto(LibraryManager.library, {
     var styleSheet = document.styleSheets[0];
     var rules = styleSheet.cssRules;
     for (var i = 0; i < rules.length; i++) {
-      if (rules[i].cssText.substr(0, 5) == 'canvas') {
+      if (rules[i].cssText.substr(0, 6) == 'canvas') {
         styleSheet.deleteRule(i);
         i--;
       }